Detachable shoe plates for large diameter drill bits

Abstract

Shoe members and drill shank members for large diameter cable drilling bits are provided with a tongue on one of the members that projects axially relative to the drill shank member and with an arcuate lip and projecting stop on the other of the members to trap the tongue and prevent radial movement of the shoe member in response to radially directed forces caused by the spinning of the bit in drilling operations. Such forces would impose shear stresses on the fastening members that extend through the shoe member and axially into the drill shank. Four embodiments are disclosed: a spudding bit, two star bits and a scow bit.

I claim: 
     
       1. An improved drill bit for gravity-drop cable drilling, the bit comprising: an elongated shank member having a bottom diametrical portion;   a shoe member with a metal shoe body and with inserts of a metal that is harder than the metal of the shoe body, some of the inserts projecting at an angle from a bottom of a toe on the shoe body, these angularly projecting inserts being operable to cut along an outer edge of a hole being drilled;   fastener means extending through the shoe member and into the shank member in an axial direction relative to the shank member for removably coupling the shoe member in a fixed position along the bottom diametrical portion of the shank member;   wherein one of the members coupled together by the fastener means has a tongue projecting axially relative to the shank member and disposed longitudinally relative to the bottom diametrical portion of the shank member; and   wherein the other of the members coupled together by the fastener means has an arcuate lip that opposes a radially outward facing side of the tongue and also has a projecting stop that opposes a radially inward facing side of the tongue to cooperate with the lip in restraining radial movement of the shoe member along the bottom diametrical portion of the shank member in response to radial shear forces encountered during cable drilling operations.   
     
     
       2. The improved drill bit of claim 1, wherein the lip and projecting stop are formed on the bottom diametrical portion of the shank member and wherein the tongue is formed on the shoe member. 
     
     
       3. The improved drill bit of claim 2, wherein: the shank member has openings on opposite sides of the bottom diametrical portion into a hollow portion; wherein the lip is divided into four angularly spaced apart arcuate sections;   wherein the tongue is annular in shape and is received against the bottom diametrical portion of the shank member between opposing arcuate sections;   wherein the bottom diametrical portion provides a projecting support; and   wherein the shoe member has a cutter blade portion extending across the projecting support.   
     
     
       4. The improved drill bit of claim 2, wherein: the bottom diametrical portion of the shank member has two cutter wings extending in opposite radial directions;   further comprising a second shoe member; and   wherein the first-mentioned shoe member and the second shoe member each have an axially projecting tongue that is received and positioned between a projecting stop and a lip on a corresponding cutter wing.   
     
     
       5. The improved drill bit of claim 1, wherein the lip and projecting stop are formed on the shoe member and wherein the tongue is formed on the bottom diametrical portion of the shank member. 
     
     
       6. The improved drill bit of claim 5, wherein: the shank member has a second bottom diametrical portion crossing the first-mentioned bottom diametrical portion, the bottom diametrical portions forming four radially extending cutter wings;   further comprising three shoe members in addition to the first-mentioned shoe member, each of the four shoe members having a lip and a projecting stop; and   wherein each cutter wing has a radially directed tongue that is received in position between the lip and the projecting stop of a respective shoe member.   
     
     
       7. The improved drill bit of claim 1, wherein: the shank member has a second bottom diametrical portion crossing the first-mentioned bottom diametrical portion to form four radially extending cutter wings;   further comprising three shoe members in addition to the first-mentioned shoe member;   wherein each shoe member is mounted at a radial extremity of a respective one of the four cutter wings to provide a cross-shaped gap in between the cutter wings; and   wherein cutter blade means with carbide metal inserts spans the cross-shaped gap to cut the center portion of the hole being drilled.   
     
     
       8. The improved drill bit of claim 1, further comprising a second shoe member; wherein the shoe members have respective heels which are spaced apart to provide a gap, the shoe members extending from their respective heels in opposite radial directions along the bottom diametrical portion of the shank member; and   wherein a central cutter blade with projecting hardened metal inserts is mounted to the bottom of the shank member in the gap to cut the center portion of the hole being drilled.   
     
     
       9. The improved drill bit of claim 1, further comprising means formed along the radially extending sides of the shoe member and along adjacent sides of the shank member to restrain the shoe member against rotation in response to torsional forces. 
     
     
       10. The improved drill bit of claim 1, wherein the first-mentioned lip is disposed at one end of the bottom diametrical portion of the shank member; and wherein the projecting stop is a second arcuate lip disposed at an opposite end of the bottom diametrical portion of the shank member.